<p>In magnetic gears, the ferromagnetic pole piece is a key component that induces the flux-modulation effect and directly affects the performance of the magnetic gear (MG). In rotary machines, mutual interference between design parameters may occur. Therefore, in this study, for a linear magnetic gear, the effects of the initial position and the horizontal (X) and vertical (Y) dimensions of the ferromagnetic pole piece on thrust force, loss, and efficiency were analyzed using FEM. The optimized model was designed to maximize thrust force and efficiency, and its performance was compared with that of the initial model. As a result, the thrust force increased by 20.8%, the efficiency decreased by 0.3%, and the thrust-force ripple increased by 1%. These results confirm that adjusting the position of the ferromagnetic pole piece within the air gap, rather than adopting a 1:1 ratio for horizontal and vertical lengths, allows the thrust force performance to be maximized.</p>